Known bugs:
-----------
- internal path field of folders is not updated correctly
  on folder movement. not critical, because this field
  is only used in the IO filter dialog for information
  only.


This is my actual TODO list:
----------------------------
- edit configuration parameters
- move mail to folder
- mark a selection of mails as read
- input filter: delete operation
- pop3 error window
- smtp error window
- when selecting last selected message in a folder, don't
  set status on read
- prevent opening several instance of the same window, if
  this makes no sense (e.g. account window)
- configure a default domain name for recipients
- empty trash
- address book
